Because I'm no longer 13 years old, I haven't really paid much attention to teenywink Canadian singing sensation Justin Bieber since he was first hammered into the collective unconscious like a nail of frozen piss into a cabbage, but I've just seen a photo of him and God, he's grown. He's now 36 years old and is played by a gangling miscast Jim Carrey action figure. And none of his costumes fit any more, which means he has to take to the stage wearing trousers that only come down to his knees and a child-size baseball cap optimistically Pritt-sticked to his hairdo.

Naturally it's left him too depressed to sing. His performances now consist of him quietly begging the audience to leave so he can have some time to himself. But they can't hear his pleas because they're too busy screaming, and they can't see his tears because they're watching his performance while filming it on their Samsungs and he's too far away for the weeping to be visible onscreen. Caught in a trap of his own making, he is the loneliest man in the world. One day he'll learn to express this in his music. And then you will love him.

The photo of Bieber accompanied an article about his mother, Pattie Mallette, who's courting controversy with a short anti-abortion film called Crescendo. She's hoping a series of screenings will raise $10m in aid of "pregnancy crisis centres". This seems unlikely, since most short films lose money, and unlike Crescendo, those aren't ideologically driven tales of abortion set in 18th-century Europe. Expecting an abortiony period drama (or, more accurately, missed-period drama) to generate millions of dollars is an act of optimism on a par with trying to pole vault over the sun. Personally, I'd downplay the gloomier aspects on the poster, change the title to something like Yipes a Doodle Doo! and maybe add a bit where a monkey drives a car.

This whole pro-life movie escapade hasn't gone down well with some. It's the latest in a series of setbacks for Bieber, who, I was horrified to learn in the past five minutes from the devastatingly trustworthy Perez Hilton website, had a bumpy start to the year. First a paparazzo died while pursuing his car. Then he was accused of smoking marijuana. Then he split from his girlfriend. Then he got his bum out on Twitter and deleted the photo moments later. Then he was accused of firing a Nerf gun at a security guard. Now his mum's made a controversial film. On top of that, he's ageing at an alarming rate. Since you started this article, he's put his crayons away and taken out a subscription to Decanter magazine.

He stands at a crossroads. But unlike teen idols of the yesterpast, he doesn't stand alone. In years gone by, teen idols would quietly fade from view, remembered only by a few hardcore devotees. The fallen star would pop up years later in an arch documentary to mutter something bitter about their former manager before stepping onstage at the Bumford Pavillion as part of a nostalgia line-up alongside Partners in Kryme and George the Hofmeister bear. But because Justin Bieber has over 30 million followers on Twitter, it's impossible for him to vanish gracefully. His fans can't gently forget him over time. They have to actively delete him. If things go badly for him, a huge percentage of the Beliebers will presumably tap "unfollow" – not all at once, but over time.

Picture the fan. It's 2021, she's at work, she's stressed, she's got a cardboard cup of coffee searing her palm, and she's trying to read a text from her boyfriend, when up pops an update from 49-year-old Bieber, griping about the waiting time at a Hertz customer service desk #aintgotalldaydudes.

It's the last straw. She forgets about the hours spent singing along to his music. Forgets the desktop wallpaper she had when she was 13. Forgets everything he once meant to her. And with a swipe of her thumb she finally, firmly, "unfollows" Zzzzwip. Thousands of miles away, killing time in the Hertz queue, Justin Bieber notices his follower count drop by one. It's been heading downwards since that incident with the Nerf gun back in Black January. Now he's down to a mere 6 million fans. It's hard on the ego, being gradually unfollowed by 24 million people over the course of several years. And so he does something bad.

He looks up the username of the woman who unfollowed him. Tweets something unpleasant about her avatar photo and says good riddance. She calls him a dickwad. He calls her a bitch. By the time he reaches the front of the queue, showbiz sites are running catty stories calling him "Justin Bitter" and mocking him for turning on fans. As a result, the man at the desk refuses to serve him. Yelling obscenities, Bieber is kicked out of the building. He tumbles down the steps, trips up and somehow, improbably, ends up accidentally sticking his entire index finger up the anus of a passing dog as he tries to break his fall. A passer-by films the whole thing on their mobile and shares it with the world. JUSTIN BEAGLER, they call him. He is disgraced. His follower count drops below zero, which ought to be impossible, but reality makes an exception. Later that night, alone, at home, he sings a song so heartbreaking you would (as pointed out earlier) love him if you heard it. But no one hears it. No one wants to know.

That's one potential future. The other is this: he reinvents himself as Justin Timberlake 2.0, ages gracefully, makes billions more dollars, and gains another 70 million followers. He designs uniforms for them and teaches them anthems. Gradually they seize control of the towns and cities. Six of them kick you to death in your own home before ransacking the contents and setting the building ablaze. Identical scenarios play out around the globe. The world is plunged into a 1,000 year reign of darkness. I'm sorry. But those are the only two possible outcomes.

•Charlie Brooker's new book I Can Make You Hate is available for £10.99 (rrp £16.99) with free UK p&p from the Guardian Bookshop. Visit guardianbookshop.co.uk or call 0330 333 6846